Adaptive control of motor vehicle powertrain

ABSTRACT

A method and system is disclosed for blending between different torque maps of a vehicle so that step changes of torque output are avoided as accelerator pedal position is changed. The invention provides different blending rates so as to reduce the blending time if driver demand is in the direction of torque change.

FIELD OF THE INVENTION

Embodiments of the present invention relate to adaptive control of apowertrain of a motor vehicle, in particular, embodiments of the presentinvention relate to adaptive control of a source of motive power, forexample an internal combustion engine and in particular; but notexclusively, to the response of the engine to an operator command inconsequence of a change of engine operating mode. The change of engineoperating mode may in turn be related to a change of operating mode of avehicle In which the engine is installed. Aspects of the inventionrelate to a method, to a system and to a vehicle.

BACKGROUND

Internal combustion engines of vehicles may have operating modes whichmay be selectable by the driver. Thus in some vehicles an economy mode,a normal mode and a sport mode may be provided, each mode having adifferent engine response to one or more commands of the driver.Typically the engine may respond differently in each mode to a giveninput of the accelerator pedal, being least responsive in economy mode,and most responsive in sport made. In this way driveability of thevehicle can be improved by providing a range of accelerator pedalmovement which is appropriate to, for example, the output torquecharacteristic of the engine. Such a system necessarily relies upon anelectronic input from the vehicle driver, for example an acceleratorpotentiometer providing an input signal to an electronic control unithaving a plurality of accelerator pedal position/output torque maps. Themaps may also be referred to as or accelerator pedal progression maps.

Another kind of operating mode relates to the terrain which a vehicle isintended to cross. U.S. Pat. No. 7,349,776, the content of which ishereby incorporated by reference, describes a vehicle control system inwhich the driver can implement improved control over a broad range ofdriving conditions, and in particular over a number of differentterrains which may be encountered when driving off-road, in response toa driver input command relating to the terrain, the vehicle controlsystem is selected to operate in one of a number of different drivingmodes including one or more terrain response (TR) modes. For each TRmode, the various vehicle subsystems are operated in a mannerappropriate to the corresponding terrain.

In one arrangement, a mode (for example a winter mode) is available inwhich the vehicle is configured to launch from standstill in a forwardgear other than first gear such as a second gear to reduce risk ofexcessive wheel slip. Different modes may have different acceleratorpedal position/output torque maps, torque delivery (accelerator pedalposition/output torque maps in combination with-a rate at whichengagement of transmission clutches is controlled to take place therebydetermining how aggressively gear shifts take place), and transmissionshift points as a function of coefficient of surface friction. Forexample, in one or more TR modes the transmission shift points may hearranged wherein gear shifts take place at lower speeds than they mightotherwise take place at, and in a more gentle manner (e.g. at a slowerrate).

When a driver selects an appropriate terrain response mode, a vehiclecontrol unit (VGU) selects a corresponding one or moreaccelerator/torque maps, for example when driving in rocky terrain, amode appropriate to travel over such terrain may be selected in whichthe accelerator pedal/output torque map generates a high torque outputfor a small accelerator movement, thus giving immediate urge to overcomea rock step. In contrast on sand, a low torque output may be indicatedfor the same accelerator movement, so as to avoid spinning the vehiclewheels and digging a hole. To some extent the selected terrain responsemode (and therefore torque map) may foe a matter of judgement by a userrelated for example to the available grip of one or more wheels of thevehicle on the terrain.

Any two torque maps associated with different respective vehicleoperating modes coincide at zero accelerator position/zero torque andmaximum accelerator position/maximum torque. In between theseconditions, If the map being used to determine engine output torque as afunction of accelerator pedal position changes, an immediate change ofengine output, torque may occur.

if an alternative operating mode is selected by the vehicle driver, achange In the characteristic of engine response is generally not asurprise—the change is in fact expected by the driver and is generallydesirable. However difficulties may arise if the operating mode isautomatically selected in response to a vehicle sensing a change ofoperating condition. Thus, for example a vehicle may detect a change ofterrain from rock to sand and, whilst the accelerator is partly applied,command the vehicle engine to adopt a different torque map. Theconsequent change in engine response may be disconcerting to the driver,especially if such automatic mode changes are repeated frequently. Theymay foe particularly disconcerting to the vehicle driver it theaccelerator is not being moved at the time of change.

FIG. 1 shows a known motor vehicle 101 having a powertrain 101 P. Thepowertrain 101P includes an engine 121, a transmission 124, a powertake-off unit (PTU) 137, a rear driveshaft or propshaft 131R and a frontdriveshaft or propshaft 131F. The rear driveshaft 131R is operable todrive a pair of rear wheels 113,114 via a rear differential 135R whilstthe front driveshaft 131F is operable to drive a pair of front wheels111, 112 via a front differential 135F.

The vehicle 101 has m engine controller 121C arranged to receive anaccelerator pedal position signal from an accelerator pedal 161 and abrakes controller 141C operable to receive a brake pedal position signalfrom a brake pedal 163.

In the configuration of FIG. 1 the transmission 124 is releasablycorrectable to the rear driveshaft 131R by means of the power transferunit (PTU) 137, allowing selectable two wheel drive or four wheel driveoperation.

The PTU 137 is also operable in a ‘high ratio’ or a ‘low ratio’configuration, in which a gear ratio between an input shaft and anoutput shaft thereof is selected to be a high or low ratio. The highratio configuration is suitable for general on-road or “on-highway”operations whilst the low ratio configuration is more suitable fornegotiating certain off-road terrain conditions and other low speedapplications such as towing.

The vehicle 101 has a central controller 1010, referred to as a vehiclecontrol unit (VCU) 101C. The VCU 101C receives and outputs a pluralityof signals to and from various sensors and subsystems provided on thevehicle 101.

The vehicle 101 has a transmission mode selector dial 124S operable toselect a required operating mode of the transmission 124, The selectordial 124S provides a control signal to a transmission controller 124Cwhich in turn controls the transmission 124 to operate according to theselected mode. Available modes include a park mode, a reverse mode and adrive mode.

The vehicle 101 also has a terrain response mode selector dial 128S. Theterrain response mode selector dial 128S is operable by a driver toselect a required terrain response mode of operation of the vehicle.

It is to be understood that if a user selects the drive mode of thetransmission 124, the engine controller 1210 employs a drive modethrottle map to determine the amount of drive torque, that the engine121 should produce as a function of accelerator pedal position, if theuser selects the sport mode of the transmission, the engine controller1210 employs a sport mode throttle map instead of the drive modethrottle map. The throttle maps differ in that the sport, mode throttlemap is arranged to provide a. more aggressive response by the engine121C to a given initial advance (such as depression) of the acceleratorpedal 181. Different respective driveability filters may also be appliedIn dependence on the selected transmission mode.

Different accelerator pedal position/output torque maps (anddriveability filters) are also employed for different respectiveuser-selectable terrain response modes.

As noted above, in some arrangements the vehicle may be operableautomatically to select an appropriate TR mode for the prevailingdriving conditions,

FIG. 2 shows two different accelerator pedal progression maps in theform of a plot of engine torque output T as a function of acceleratorpedal position P on a scale from 0 to 100% of full scale depression ofthe accelerator pedal 161.

FIG. 2 shows two extreme vehicle operating modes A,B. Mode A is acautious torque map and may correspond for example to a TR mode suitablefor use when driving over sand. Mode B is a more aggressive torque mapand may correspond to a TR mode suitable for use when driving over rock.A driver may select operation according to mode A or mode B by means ofthe TR mode selector dial 128S. At the zero and 100% acceleratorpositions, the torque maps coincide, but at part depression of theaccelerator pedal 161 significant differences in torque output areapparent.

Thus a switch from mode A to mode S at point C (50% application ofaccelerator pedal) results in an immediate jump to point D, withconsequent increase In engine torque output The characteristic of line 8is subsequently followed. A corresponding switch in the reversedirection results in significant drop in output torque. Changes betweentorque maps generally comprise movements in the direction of the y axis.

The change in output torque of the engine may take time, and can bedeliberately blended, as illustrated In FIG. 8. FIG. 3 is a plot ofoutput torque as a function of time during blending from mode A to modeB at point C. Thus the increase from point C to point D may becontrolled to avoid a step change. For example a maximum blending rate,say 7 Nm/s may be applied, and/or blending may take place at a definedrate within a maximum time period, of say 20 seconds. A small torquechange will blend quickly, and a large torque change will take longer.

During a long period of blending from one torque characteristic toanother, the vehicle driver may wish to move the accelerator pedal 181to demand more or less torque from the vehicle engine 121. It would bedesirable to minimize the changeover time commensurate with the changingdemands of the vehicle driver.

It is against this background that the present invention has beenconceived. Aspects and embodiments of the invention may provide asystem, a method and a vehicle in which blending Is improved. Other aimsand advantages of aspects and embodiments of the present Invention willbecome apparent from the following description, claims and drawings.

SUMMARY OF THE INVENTION

According to a first aspect of the invention for which protection issought there is provided a method of blending between differentcharacteristics of accelerator pedal position and output torque in avehicle, the method comprising the steps of:

-   -   detecting a first operating mode of a vehicle and applying a        source characteristic;    -   detecting a change of operating mode of the vehicle and        selecting a target characteristic;    -   blending the characteristic applied from the source        characteristic to the target characteristic at a base blending        rate, said blending rate being increased if during blending the        position of the accelerator pedal is moved in the direction of        torque change due to blending.

According to a second aspect of the invention for which protection issought there is provided a method of blending between differentcharacteristics of accelerator position and output torque in a vehicle,the method comprising the steps of:

-   -   defecting a first operating mode of a vehicle and applying a        source characteristic;    -   detecting a change of operating mode of the vehicle and        selecting a target characteristic;    -   blending the characteristic, applied from the source        characteristic to the target characteristic at a base blending        rate, said blending rate being reduced if during blending the        position of the accelerator pedal is not substantially moved, or        is moved in oppositely to the direction of torque change due to        blending.

The characteristic relating accelerator pedal position to output torquemay directly indicate the torque output at the flywheel of an internalcombustion engine, or may represent an analogue thereof, such as one ormore of drive torque at the vehicle wheels, power output, anothermeasure of tractive effort fuel flow, airflow or any measurableindicator that varies accordingly to accelerator pedal progression andtorque output. The output torque may represent the output of other formsof motive power, such as an electric motor, or an analogue thereof, suchas motor current. Where the vehicle is a hybrid vehicle in which morethan one source of propulsion may operate in parallel, output torque maycorrespond to a net torque, delivered to a powertrain by an engine andone or more electric propulsion motors.

Many suitable analogues are known, so that whilst output torque is aconvenient direct measure, the Invention does not exclude the use of oneor more analogues to define the changing pedal progressioncharacteristic.

Thus according to embodiments of the invention, a change in torquedemand, due to a change of vehicle operating mode, to a targetcharacteristic, will be completed comparatively quickly if during thetransition the vehicle driver re-positions the accelerator pedal in thedirection of the changing torque demand.

Embodiments of the invention reflect that a vehicle driver will be lessdisconcerted by a changing torque output due to mode change, if theintention of the driver is In the direction of changing torque output.

In the first aspect of the Invention described above, the base blendingrate may be zero or positive, and the increased rate will be a greatervalue. In the second aspect of the invention described above, the baseblending rate will be positive, and the reduced rate will be a lesserrate, or zero.

Embodiments of the present invention can be implemented in several ways.In one method a base blending rate is applied when a change in outputtorque due to a mode change is required, and driver torque demandchanges in the direction of the change of torque. A reduced blendingrate is applied for a substantially unchanging driver demand and forchanges In driver torque demand that occur in the opposite direction tothe blend.

In an alternative a base blending rate is applied when a change inoutput torque due to a mode, change takes place accompanied bysubstantially unchanging driver demand or by a driver demand opposite tothe direction of the change in torque. An increased blending rate isapplied for driver demand In the direction of the change.

in another alternative a standard blending rate may be determined, andincreased and/or reduced rates of blending applied according to thedirection of driver demand in relation to the change of output torquedue to mode change.

A fixed base blending rate may be applied for all pedal progression(torque) characteristics, but preferably the base blending rate isselected according to the particular source and target maps. For examplethe base blending rate may be varied according to the difference betweenthe source and target torque at the instant pedal position, a greaterrate being applied where the difference is greater. Furthermore the baseblending rate may be varied according to the position of the acceleratorpedal, so that different rates may apply as the pedal moves from fullyclosed to fully open. These different rates may for example be retainedin a look-up table by reference to torque map and accelerator pedalposition.

Likewise, the changed blending rate (increased or reduced) may bediscrete or defined as a percentage of the base blending rate, or bechanged according to the difference between the torque maps, oraccording to the instant position of the accelerator pedal it is to beunderstood that reference to percentage is directly equivalent toreference to a proportion, In contrast with a fixed absolute value thatis not a proportion of another value.

In the case of analogues of output torque, the skilled man will identifyparameters to give an equivalent effect, to the intent that blending ismore quickly completed if driver demand is in the direction of thechange in output torque (or the selected analogue thereof).

In one embodiment of the invention, the change in blending rate due to aparticular condition and instant position of the accelerator pedal islinked to the instant torque difference between the source and targettorque characteristics.

Thus an increased rate of blend consequent upon driver demand in thedirection of the blend may be a step change, for example a rate increasein the range 30-100%, during the period of Increased rate. Preferablyhowever the rate increase is proportional to the instant torquedifference so that a high rate is applied for a large torque difference,and this rate is gradually reduced as the torque difference reduces. Therate may vary according to the instant position of the acceleratorpedal.

According to a further aspect of the invention there is provided anelectronic control system of a vehicle, for blending between differentcharacteristics of accelerator pedal position and output torque byreference to a plurality of torque maps held within a memory, saidsystem being adapted to detect a first operating mode of the vehicle andapply a source torque man, detect a change of operating mode of thevehicle and select a target torque map, and blend the torque map appliedfrom said source torque map to said target torque map at a base blendingrate, said base blending rate being increased if the torque change dueto blending is In the direction of driver demand.

Optionally, in addition or instead, the blending rate may be reduced ifduring blending the position of the accelerator pedal is notsubstantially moved, or is moved oppositely to the direction of torquechange due to blending.

Furthermore, an aspect of the invention provides a vehicle having suchan electronic control system and a system of automatically changingoperating mode in response to different conditions of use, such as achange of terrain.

Within the scope of this application it Is expressly intended that thevarious aspects, embodiments, examples and alternatives set out in thepreceding paragraphs, in the claims and/or in the following descriptionand drawings, and in particular the individual features thereof, may betaken independently or in any combination. For example, featuresdescribed in connection with one embodiment are applicable to allembodiments unless such features are incompatible.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way ofexample only, with reference to the accompanying drawings in which:

FIG. 1 is a schematic illustration of a known motor vehicle;

FIG. 2 and FIG. 3 illustrate graphically blending of torque betweendifferent operating modes of a vehicle;

FIG. 4 is a schematic illustration of a motor vehicle according to anembodiment of the present invention; and

FIG. 5 and FIG. 6 illustrate modified blending according to anembodiment of the present invention; and

FIGS. 7 to 11 illustrate the effect of embodiments of the invention fora method of increased blending rate with corresponding change of driverintention;

DETAILED DESCRIPTION

FIG, 4 is a schematic illustration of a motor vehicle 201 according toan embodiment of the present invention. Like features of the vehicle 201of FIG. 4 to those of the vehicle 101 of FIG. 1 are shown with likereference numerals prefixed numeral 2 instead of numeral 1. Thus engine121 of the vehicle 101 of FIG. 1 corresponds to engine 221 of thevehicle 201 of FIG. 4.

The vehicle 201 has a VCU 201 programmed with accelerator pedalprogression maps that are used to determine engine torque T as afunction of accelerator pedal position P,

FIG. 5 is a plot of engine torque (T) against time(t) over a period ofchanging accelerator pedal position for the vehicle 201 of FIG. 4. Twovehicle modes M1, M2 are illustrated, each mode having a differentoutput torque from the engine 221 in response to a given acceleratorpedal position. Mode M1 may be characterised as cautious, correspondingto program A of FIG. 1, whereas mode M2 corresponds to program B of FIG.1, and is more aggressive.

Accelerator pedal position is not shown, but torque increases anddecreases can be assumed to follow a similar change to accelerator pedalposition.

Thus at time t₀, the accelerator pedal 161 is not advanced (and istherefore in a substantially released position, at a substantiallyundepressed or neutral position) and engine torque output may beconsidered to he substantially zero even if the engine 221 is running atidle speed.

At t₁ the accelerator pedal position is advanced. Two possible torquepaths are possible, following the traces M1 and M2, depending on whethermode M1 or mode M2 are selected. The vehicle is assumed to be in mode M1so that output torque follows the trace M1.

At t₂, movement of the accelerator pedal 161 is paused, and inconsequence there is no further rise in engine output torque.

At t₃, the VCU 201C automatically changes the mode of operation of thevehicle to mode M2, for example due to detection of a change of terrainby means not described here. Blending of engine output, torque T to thatrequired for operation in mode M2 commences at a fixed base ratedetermined empirically as the maximum rate which a vehicle driver willaccept without becoming disconcerted during an automatic mode change.

At t₃, the instant torque (mode M1) is about 80 Nm, and the targettorque (mode M2) is about 200 Nm. The difference is thus 120 Mm, and atypical base blending rate is 7 Nm/s although other values may be usedinstead. If accelerator position remains unchanged, blending from M1 toM2 at the base rate will thus take about 17 seconds, in this example.

After t₃ the angina output torque T, shown by trace E in FIG. 5, thusbegins progressively to increase above the trace of mode M1.

At t₄ the accelerator pedal position is retracted: engine output torquereduces in consequence, but blending at the base rate continues so thatwhen the accelerator pedal is paused at t₅ a further upward divergenceof trace E from trace M1 is apparent.

The accelerator pedal 181 is paused until t₆, and further upwarddivergence at the base blending rate is apparent in this period.

At t₆ the accelerator pedal 161 is again advanced. Since driver demandfor increased torque Is in the direction of blending from M1 to M2, therate of blending is increased above the base blending rate, so that bythe time the accelerator pedal is again paused at t₇, engine outputtorque T has rapidly approached M2. Thus in this example, the periodfrom t₅ to t₆ at the base blending rate provided for about 25% ofblending to be completed. The shorter period from t₆ to t₇ at theincreased blending rate allowed blending to reach about 80% completion.

At t₇ the accelerator pedal is again paused, and blending is resumed atthe base blending rate. If no further change of accelerator position ismade before blending is completed, the time for blending will havereduced from about 17 seconds to about 12 seconds.

Similarly, as shown in FIG. 6, a change in vehicle mode at time t₆ to amore cautious engine torque map (from map M2 to map M1) causes blendingat the base rate from t₈ to t₉—in this period the accelerator pedalposition is not changing.

At t₁₀, the accelerator pedal 261 is backed-off, to demand a lowertorque from the engine 221, Since this action is in the direction ofmode change from M2 to M1, the base blending rate is increased, so thatby when movement of the accelerator pedal 261 is paused, 50% of theblend is completed.

After t₁₀, blending continues at the base rate, and does so during aperiod of an advancing accelerator pedal position from t₁₁ to t₁₂, andat a paused position after t₁₂.

Special measures may be employed when the accelerator pedal is movedrapidly towards the maximum and minimum positions. In this case, in thevehicle 201 of the embodiment of FIG. 4 if the pedal 261 is advanced toa maximum position (which may be defined as greater than 95% of fulltravel of the accelerator pedal 261) at a rate greater than a prescribedrate, the VCU 201C is arranged to command substantially immediately theapplication of substantially the full amount of engine torque Tcorresponding to position U of FIG. 2.

In some embodiments, blending is determined by the VCU 201C to becomplete substantially immediately when the accelerator pedal 281 isadvanced to the maximum position (corresponding to position U) orretreated to the minimum position (which may be defined as less than 5%of the full travel of the accelerator pedal 261 and corresponds toposition L). No further blending is therefore required, and furtheraccelerator pedal movement results in engine response according to themode trace to which blending was being performed. The prescribed ratesfor advancement or backing of the pedal 261 maybe substantially the sameor different.

In the embodiment of FIG. 4, if blending is still incomplete when theaccelerator pedal 261 is advanced to the maximum position or backed tothe minimum position, the VCU 201C may be configured to apply maximum orminimum available torque respectively, but blending may continue at aprescribed rate (such as the base blending rate) whilst the pedal is atthe maximum or minimum positions. If however the pedal is subsequentlymoved away from the maximum or minimum positions, before blending iscomplete, the blending rate may be increased if the pedal is moved inthe direction of blending, as described above.

It will be appreciated that definition and recognition of the minimumand maximum accelerator positions may be selected according to thenature and precision of the accelerator pedal mechanism, and inparticular to the accuracy, noise and hysteresis present in the outputof a potentiometer indicative of pedal position. Selection andadjustment of these parameters is within the ability of an appropriatelyskied person.

Likewise, the rate of change of accelerator pedal position may be sensedin some embodiments in order to determine whether movement to themaximum and minimum positions is in progress, and thereby give an earlyindication that engine output torque should be maximized or minimizedsubstantially immediately.

In the present embodiment illustrated in FIG. 4, a method of blending isimplemented whereby the blending rate is increased when driver demand isin the direction of blend. The same effect may be realized in a methodwhere blending rate is reduced, typically to zero, when driver demand isunchanging or opposite to the direction of blend.

These two methods may be combined so that a base blending rate isapplied for a substantially constant position of accelerator pedal, isincreased when driver demand is in the direction of blend, and isreduced when driver demand is opposite to the direction of blend.

FIGS. 7 to 10 illustrate the effect of one embodiment of the inventionin which the rate of blending is increased when driver intention is tochange the amount of engine torque in the direction of the blend.

FIG. 7 is a plot of vehicle mode as a function of time. The plotindicates a change of mode from M1 to M2 at time t₁₃. Mode M2corresponds to trace B of FIG. 2 and is a more aggressive torque mappingthan mode M1, which corresponds to trace A of FIG. 2.

FIG. 8 is a plot of accelerator pedal position as a function of timebetween two exemplar positions or levels P1, P2 between 0 and 100% offull travel of the accelerator pedal 261. At time t₁₄ a backingaccelerator is advanced, and at t₁₅ a steady condition is assumed. Att₁₆ backing is again initiated until a steady state is reached at t₁₇.

FIG. 9 is a plot of blending rate B′ as a function of time. If can beseen that at the moment the mode change is initiated, a base blendingrate B′base is applied. B′base is substantially equal to half themaximum available blending rate B′max that may be applied in the presentembodiment although other proportions or other absolute values are alsouseful. The base blending rate is applied between time t₁₃ and time t₁₄whilst the accelerator pedal 261 is not advancing.

Between times ₁₄ and t₁₅, the maximum blending rate B′max is applied,whilst the accelerator pedal position is advancing. During the periodfrom t₁₅ to t₁₆ the accelerator pedal is substantially stationary whilstduring the period from t₁₅ to t₁₇ the accelerator pedal 261 is backed(moved towards a less depressed position). From time t₁₇ the acceleratorpedal 261 remains substantially stationary. Accordingly, the VCU 201Creduces the blending rate from B′max to B′base during the period from inonwards, until blending is complete at time t₁₈ as described below.

FIG. 10 is a plot of percent completion of blending B_(T) as a functionof time, it can fee seen that the rate of blending increasessignificantly between times t₁₄ and t₁₅ compared with the base ratebefore and after this period, which reduces the overall time forcompletion of blending from M1 to M2. Blending can be seen to becomplete at time t₁₈.

FIG. 11 is a plot of percent completion of blending B_(T) for anembodiment in which the blending rate B′ remains substantially equal toa base blending B′base throughout the period during which blending takesplace. It can be seen that the time required to complete blendingbetween modes M1 and M2 is much longer than that in the ease of theembodiment described with respect to FIGS. 7 to 10, having the blendingrate profile of FIG. 9. In the embodiment illustrated in FIG. 11, thebase blending rate B′base is initiated at t₁₃, so that the engine torquemapping gradually changes to meet M2. At time t18 blending is stillincomplete as can be seen from FIG. 11.

Embodiments of the present invention have the advantage that blendingcan be completed more quickly than in some alternative systems. This isat least in part because the blending rate may be varied according tomovement of the accelerator pedal by the driver. In some embodiments, ifthe accelerator pedal 261 is moved in the direction of torque change dueto the mode change, the blending rata may be Increased. Alternatively orin addition if the accelerator pedal 261 is held stationary or moved ina direction against the direction of torque, change due to the modechange, the blending rate may be reduced, optionally substantially tozero.

Embodiments of the present invention may he understood by reference tothe following numbered paragraphs:

1. A method of blending between different characteristics of acceleratorposition and output torque in a vehicle, the method comprising:

-   -   detecting a first operating mode of a vehicle and applying a        source characteristic;    -   detecting a change of operating mode of the vehicle and        selecting a target characteristic,    -   the method comprising blending the characteristic applied from        said source characteristic to the target characteristic at a        base blending rate, said blending rate being increased if during        blending the position of the accelerator pedal is moved in the        direction of torque change due to blending, and/or    -   blending the characteristic, applied from the source        characteristic to the target characteristic, at a base blending        rate, said blending rate being reduced if during blending the        position of the accelerator pedal is not substantially moved, or        is moved oppositely to the direction of torque change due to        blending.

2. A method accordingly to paragraph 1, wherein the base blending rateis non-zero.

3. A method according to paragraph 1, and including the further step ofre-adopting said base blending rate if the position of the acceleratorpedal is not changed or is moving oppositely to the direction of torquechange.

4. A method according to paragraph 1, and including the further step ofre-adopting said base blending rate if the position of the acceleratorpedal is moved in the direction of torque change.

5. A method according to paragraph 1, wherein said base blending rate isvariable according to the difference between a source characteristic anda target characteristic.

6. A method according to paragraph 1, wherein the increase in saidblending rate is variable according to the difference between a sourcecharacteristic and a target characteristic.

7. A method according to paragraph 1, wherein the reduction in saidblending rate is variable according to the difference between a sourcecharacteristic and a target characteristic.

8. A method according to paragraph 1, wherein said base blending rate isincreased or reduced by a percentage thereof.

9. A method according to paragraph 1, wherein the amount by which thebase blending rate is increased or reduced is dependent upon the instantposition of said accelerator pedal.

10. An electronic control system of a vehicle, for blending betweendifferent characteristics of accelerator pedal position and outputtorque by reference to a plurality of torque maps held within a memory,said system being adapted to detect a first operating mode of thevehicle and apply a source torque map, detect a change of operating modeof the vehicle and select a target torque map, and blend the torque mapapplied from said source torque map to said target torque map at a baseblending rate,

-   -   wherein said base blending rate is increased if the torque        change due to blending is in the direction of driver demand,        and/or    -   wherein said base blending rate is reduced if the torque change        due to blending is not in the direction of driver demand.

11. A system according to paragraph 10, wherein said base blending rateis determined according to the difference between said source map andsaid target map.

12. A system according to paragraph 10, wherein said base blending rateis determined according to the instant position of the acceleratorpedal.

13. A vehicle having a control system according to paragraph 10, and asystem for automatically changing operating mode of a vehicle accordingto different conditions of use, whereby one of a plurality of torquemaps is selected for each operating mode.

Throughout the description and claims of this specification, the words“comprise” and “contain” and variations of the words, for example“comprising” and “comprises”, means “including but not limited to”, andis not intended to (and does not) exclude other moieties, additives,components, integers or steps.

Throughout the description and claims of this specification, thesingular encompasses the plural unless the context otherwise requires.In particular, where the indefinite article is used, the specificationis to be understood as contemplating plurality as well as singularity,unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties orgroups described in conjunction with a particular aspect, embodiment orexample of the invention are to be understood to be applicable to anyother aspects embodiment or example described herein unless incompatibletherewith.

1. A method of blending between different characteristics of acceleratorposition and output torque in a vehicle, the method comprising:detecting a first operating mode of a vehicle and applying a sourcecharacteristic; detecting a change of operating mode of the vehicle andselecting a target characteristic; blending the characteristic appliedfrom said source characteristic to the target characteristic at a baseblending rate, said blending rate being increased if during blending theposition of the accelerator pedal is moved in the direction of torquechange due to blending.
 2. A method of blending between differentcharacteristics of accelerator position and output torque in a vehicle,the method comprising: detecting a first operating mode of a vehicle andapplying a source characteristic; detecting a change of operating modeof the vehicle and selecting a target characteristic; blending thecharacteristic applied from the source characteristic to the targetcharacteristic at a base blending rate, said blending rate being reducedif during blending the position of the accelerator pedal is notsubstantially moved, or is moved oppositely to the direction of torquechange due to blending.
 3. A method according to claim 1, wherein thebase blending rate is non-zero.
 4. A method according to claim 1, andincluding the further step of re-adopting said base blending rate if theposition of the accelerator pedal is not changed or is moving oppositelyto the direction of torque change.
 5. A method according to claim 2, andincluding the further step of re-adopting said base blending rate if theposition of the accelerator pedal is moved in the direction of torquechange.
 6. A method according to claim 1, wherein said base blendingrate is variable according to the difference between a sourcecharacteristic and a target characteristic.
 7. A method according toclaim 1, wherein the increase in said blending rate is variableaccording to the difference between a source characteristic and a targetcharacteristic.
 8. A method according to any of claim 2, wherein thereduction in said blending rate is variable according to the differencebetween a source characteristic and a target characteristic.
 9. A methodaccording to claim 1, wherein said base blending rate is increased by apercentage thereof.
 10. A method according to claim 1, wherein theamount by which the base blending rate is increased dependent upon theinstant position of said accelerator pedal.
 11. An electronic controlsystem of a vehicle, for blending between different characteristics ofaccelerator pedal position and output torque by reference to a pluralityof torque maps held within a memory, said system being adapted to detecta first operating mode of the vehicle and apply a source torque map,detect a change of operating mode of the vehicle and select a targettorque map, and blend the torque map applied from said source torque mapto said target torque map at a base blending rate, said base blendingrate being increased if the torque change due to blending is in thedirection of driver demand.
 12. An electronic control system of avehicle, for blending between different characteristics of acceleratorpedal position and output torque by reference to a plurality of torquemaps held within a memory, said system being adapted to detect a firstoperating mode of the vehicle and apply a source torque map, detect achange of operating mode of the vehicle and select a target torque map,and blend the torque map applied from said source torque map to saidtarget torque map at a base blending rate, said base blending rate beingreduced if the torque change due to blending is not in the direction ofdriver demand.
 13. A system according to claim 11, wherein said baseblending rate is determined according to the difference between saidsource map and said target map.
 14. A system according to claim 12,wherein said base blending rate is determined according to the instantposition of the accelerator pedal.
 15. A vehicle having a control systemaccording to claim 11, and a system for automatically changing operatingmode of a vehicle according to different conditions of use, whereby oneof a plurality of torque maps is selected for each operating mode.
 16. Avehicle having a control system according to claim 12, and a system forautomatically changing operating mode of a vehicle according todifferent conditions of use, whereby one of a plurality of torque mapsis selected for each operating mode.
 17. A method according to claim 2,wherein said base blending rate is reduced by a percentage thereof. 18.A method according to claim 2, wherein the amount by which the baseblending rate is reduced dependent upon the instant position of saidaccelerator pedal.
 19. A method according to claim 2, further comprisingthe step of operating the vehicle using the blended characteristic. 20.A method according to claim 1, further comprising the step of operatingthe vehicle using the blended characteristic.